Hantavirus Pulmonary Syndrome

Hantavirus pulmonary syndrome (HPS) is an infectious disease characterized by flu-like symptoms that can progress rapidly to potentially life-threatening breathing problems. Several types of hantaviruses can cause hantavirus pulmonary syndrome, and they are carried by several types of rodents, particularly the deer mouse. You become infected primarily by breathing air infected with hantaviruses that are shed in rodent urine and droppings.

Because treatment options are limited, the best protection against HPS is to avoid rodents and their habitats.

Symptoms

HPS advances through two distinct stages. In the first stage, you may experience flu-like signs and symptoms that may include:

Fever and chills

Headaches and muscle aches

Vomiting, diarrhea, or abdominal pain

In its early stages, hantavirus infection is difficult to distinguish from influenza, pneumonia, or other viral conditions. After four to 10 days, more-serious signs and symptoms begin that typically include:

A cough that produces secretions

Shortness of breath

Fluid accumulating within the lungs

Low blood pressure

Reduced heart efficiency

How People Get HPS

Cases of HPS occur sporadically, usually in rural areas where forests, fields, and farms offer suitable habitat for the virus’s rodent hosts. The peridomestic setting (for example, barns, outbuildings, and sheds) are potential sites where people may be exposed to the virus. In the U.S. and Canada, the Sin Nombre hantavirus is responsible for the majority of cases of HPS. The host of the Sin Nombre virus is the deer mouse (Peromyscus maniculatus), present throughout Western and Central U.S. and Canada.

How Humans Become Infected with HPS

In Montana, the deer mouse (found throughout Montana) and the white footed mouse (found in Eastern Montana) are the reservoir of the virus. The rodents shed the virus in their urine, droppings, and saliva. The virus is mainly transmitted to people when they breathe in air contaminated with the virus.

When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air. This process is known as “airborne transmission”.

There are several other ways rodents may spread hantavirus to people:

If a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare.

Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.

Researchers also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.

The types of hantavirus that causes HPS in the U.S. cannot be transmitted from one person to another. For example, you cannot get the virus from touching or kissing a person who has HPS or from a health care worker who has treated someone with the disease. You also cannot get the virus from a blood transfusion in which the blood came from a person who became ill with HPS and survived.

People at Risk for HPS

Anyone who comes into contact with rodents that carry hantavirus is at risk of HPS. Rodent infestation in and around the home remains the primary risk for hantavirus exposure. Even healthy individuals are at risk for HPS infection if exposed to the virus.

Potential Risk Activities for HPS

Opening or cleaning cabins, sheds, and outbuildings, including barns, garages, and storage facilities that have been closed during the winter is a potential risk for hantavirus infections, especially in rural settings.

Cleaning in and around your own home can put you at risk if rodents have made it their home too. Many homes can expect to shelter rodents, especially as the weather turns cold. Please see our prevention information on how to properly clean rodent-infested areas.

Construction, utility and pest control workers can be exposed when they work in crawl spaces, under houses, or in vacant buildings that may have a rodent population.

Campers and hikers can also be exposed when they use infested trail shelters or camp in other rodent habitats.

The chance of being exposed to hantavirus is greatest when people work, play, or live in closed spaces where rodents are actively living. However, recent research results show that many people who have become ill with HPS were infected with the disease after continued contact with rodents and/or their droppings. In addition, many people who have contracted HPS reported that they had not seen rodents or their droppings before becoming ill. Therefore, if you live in an area where the carrier rodents, such as the deer mouse, are known to live, take sensible precautions, even if you do not see rodents or their droppings.

Got Mice?

Here’s what you can do:

Seal Up! Seal up holes inside and outside the home to prevent entry by rodents. Mice can squeeze through a hole the size of a nickel, and rats can squeeze through a hole the size of a half dollar! Prevent rodents from entering the home by checking inside and outside the house for gaps or holes.

Trap Up! Trap rodents around the home to help reduce the rodent population. Choose an appropriate snap trap. Traps for catching mice are different from those for catching rats. Carefully read the instructions before setting the trap.